The Effects of Caffeine on Human Spinal Motoneurons

Temple University20 enrolled

Overview

This study evaluates the effects of orally ingested, commercially available, coffee (3 mg/kg of caffeine) on the excitability of human spinal motoneurons of the lower leg.

Recently, it has been shown that human spinal motoneurons do not simply act as a binary control system. Instead, they are regulated by intrinsic properties that can elicit lingering effects on the descending motoneuron. Caffeine, one of the world's most popular over-the-counter supplements, can potentially augment these characteristics of motoneurons. Using decomposition software and non-invasive, high-density surface electromyography, it is possible to extract the characteristics of these motoneurons. This project will utilize a double-blind, inactive-placebo controlled, crossover design study to examine and quantify the effects of caffeine on motoneuron excitability.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

DOUBLE

Enrollment

Conditions

Healthy

Interventions

CoffeeDIETARY_SUPPLEMENT

Starbucks brand "Via" instant coffee. (Caffeine Content: 3 mg / kg)

Decaffeinated coffeeDIETARY_SUPPLEMENT

Starbucks brand "Via" instant decaffeinated coffee. (Caffeine Content: 15 - 25 mg)

Eligibility

Sex: ALLMin age: 18 YearsMax age: 70 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: ● Between 18 and 70 years of age Exclusion Criteria: * Significant neurological or orthopedic injuries, which may limit volitional torque generation in the tested muscles. * Significant change in the subjects' health or treatment in the past month. * Known history of cardiovascular pathology (to include: uncontrolled hypertension, cardiac arrhythmias) or medical restrictions to caffeine ingestion. * Allergies or dislike of coffee. * Women who are pregnant will be excluded due to potential forces at trunk from pelvic safety harness and due to potential adverse effects of caffeine on the developing child. * Women who are breastfeeding will be excluded due potential adverse effects on the breastfeeding infant from caffeine administration. * Adults unable to consent, minors, pregnant women, and prisoners will not be included.

Locations (1)

Temple University

Philadelphia, Pennsylvania, United States

Outcomes

Primary Outcomes

Motoneuron excitability (Delta-f)

Changes in motorneuron excitability, as quantified by Delta-F values. A paired motor unit technique will be utilized (Gorassini et al., 2002). (Typically, these values range from -5 to +10).

Time frame: Measured repeatedly at set intervals; Pre-Intervention & 30, 60, 90 minutes post-Intervention

Secondary Outcomes

Motor Unit Discharge Rate

Changes in motor unit discharge rate. This is a single value that ranges from, approximately, 0 to 30.

Time frame: Measured repeatedly at set intervals; Pre-Intervention & 30, 60, 90 minutes post-Intervention

Coherence

Changes in coherence values. Coherence provides a normalized value of the strength of correlation in the frequency domain. The magnitude of the correlation of the Fourier transforms of two spike trains is squared producing a value between 0 and 1, with 1 corresponding to a perfect linear prediction at a particular frequency (Rosenberg et al., 1989). This will be calculated using the composite spike train (Negro \& Farina, 2012) and, finally, z-transformed to allow for between-trial comparisons.

Time frame: Measured repeatedly at set intervals; Pre-Intervention & 30, 60, 90 minutes post-Intervention

Motor Unit Recruitment Threshold

Changes in motor unit recruitment threshold. As assessed by determining the amount of force (percentage of maximum volitional force output) needed to recruit an individual motor unit.

Time frame: Measured repeatedly at set intervals; Pre-Intervention & 30, 60, 90 minutes post-Intervention

Data from ClinicalTrials.gov

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